COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Stantec L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2012 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Summary of 2012 Annual Monitoring and Sampling February 1, 2013 west only. During the 2Q12, the TPHd plume was delineated to the northwest only. During the 3Q12, the TPHd plume was delineated to the northwest and south only. During the 4Q12, the TPHd plume was delineated, except to the east and north. 5.7.3 TPHo Concentrations of TPHo are generally detected on the Delta View apartment property, Water Front Towers' parking lot, and sporadically south of the Mormon Sough and in the L&M OU property. During 1Q12, the TPHo plume was delineated to the northwest only, except for detections north of the Water Front Towers' parking lot (MW-57 and MW-58). During 2Q12, the TPHo plume was delineated, except for detections south of the Mormon Slough (MW-32) and north of the UOU property (MW-59). During 3Q12, the TPHo plume was delineated to the north, northeast, and south, except for a detection north of the UOU property (MW-59). During 4Q12, the TPHo plume was delineated to the north only. 5.7.4 Benzene Low concentrations of benzene are generally detected sporadically over the Site. Benzene was detected on the northeastern side of the Water Front Towers' parking lot. Based on data collected historically and during 2012, the benzene plume is defined to the Water Front Tower's parking lot and the L&M OU property; detections of benzene occurred in wells MW-58 (1Q12) and MW-42 (4Q12). Benzene has historically been centered in the vicinity of wells MW-17, MW-43, MW-47 through MW-50, and MW-52; however, these wells were not sampled during 2012 due to measurable SPH or sheen present in the wells. 5.7.5 MtBE During 1Q12, 2Q12, and 3Q12, concentrations of MtBE are detected in two distinct areas of the Site, on the eastern portion of the Water Front Towers' parking lot, including MW-59, and southwest of the Mormon Slough including MW-44. On the Water Front Towers' parking lot and MW-59, the MtBE plume was generally delineated, except to the northeast (1Q12) and east (2Q12). To the southwest of the Site, in the Mormon Slough and MW-44, the MtBE plume was delineated, except to the southwest. During 4Q12, concentrations of MtBE were not detected at or above the MRL in the B-Zone wells, therefore, MtBE was delineated 5.7.6 TBA Concentrations of TBA was not detected at or above the MRL during 2012 in the B-Zone wells, therefore, TBA was delineated. 5.8 C-ZONE ISOCONCENTRATION TRENDS C-Zone isoconcentration trends are discussed below. Figures from the 1Q12, 2Q12, and 3Q12 are provided in Appendix K. 5.8.1 TPHg Concentrations of TPHg are generally detected on the L&M OU property and seldom on the Water Front Towers' parking lot and Delta View apartment property. Based on data collected I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 5.5